Polylactone foams and methods of making the same

ABSTRACT

The present invention is directed to compositions comprising polylactone melt, extrudate, and processes for producing a foam. In exemplary embodiments of the present invention, the processes comprise: heating a polylactone composition containing a biobased polylactone in a reaction vessel; and subjecting the polylactone composition to molding to give a foamed structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationNo. 62/697,712, filed Jul. 13, 2018, which is hereby incorporated byreference in its entirety.

FIELD

This invention generally relates to compositions and processes forproducing polymer foams. More specifically, the present invention isdirected to polylactone-based foam compositions and methods forproducing the same. Advantageously, the compositions and processes areuseful for the production of a variety of biobased products.

BACKGROUND

Polymeric foams made up of polymer chains dispersed by a gas form voids,also known as cells, between the polymer chains. By replacing solidplastic with voids, polymeric foams use fewer raw materials than solidplastics for a given volume. Thus, by using polymeric foams instead ofsolid plastics, material costs can be reduced in many applications.Additionally, foams are useful in applications as insulators and/orsealants.

Polylactones, such as polypropiolactone, polylactide, polyglycolide, andpolycaprolactone, are generally biodegradable aliphatic polyesters whichmay be made up of biobased monomers. The polylactones are generallystable, have low toxicity, and may be easily transported and stored atremote locations. Recent advances in the carbonylation of epoxides (see,e.g., U.S. Pat. No. 6,852,865) and the ring-opening polymerization ofbeta-propiolactone intermediates have provided more efficient andversatile synthetic routes to polylactones. These recent advances inproduction combined with beneficial physical and chemical propertiesmake polylactones ideal for many commercial and industrial applications.

Currently, polymer foams are commonly made using a continuous processwhere a blowing agent and a molten resin are extruded under pressurethrough an appropriate die into a lower pressure atmosphere. See US2012/0009420. Alternatively, in a batch or staged process, componentssuch as a polymer and a blowing agent are expanded to a foam by heatingto a temperature near or above a glass-transition or crystal-melttemperature. The blowing agents more commonly used for makingthermoplastic polymer foams are hydrocarbons, chlorinated hydrocarbons,hydrochlorofluorocarbons, hydrofluorocarbons, or combinations thereof.

Therefore, a need exists not only to make foams which minimize theaccumulation of solid waste, but also to produce biobased and/orcompostable foams using alternative methods are that are commerciallyviable and efficient.

BRIEF SUMMARY

The present invention solves these needs by providing polylactone-basedfoams and processes for production. Preferred embodiments are directedto polylactone foams comprising at least one polylactone polymer. Incertain preferred embodiments, the polylactone polymer comprises atleast one beta-lactone monomer. In certain preferred embodiments, thepolylactone polymer comprises two or more beta-lactone monomers. Incertain embodiments, at least one beta-lactone monomer isbeta-propiolactone. In certain preferred embodiments, at least onepolylactone polymer is polypropiolactone.

In preferred embodiments, provided are processes for producing apolylactone-based foam. In certain preferred embodiments, the processescomprise: polymerizing at least one beta-lactone monomer to produce atleast one polylactone; and blowing at least one polylactone to producethe polylactone-based foam. In certain preferred embodiments, theprocesses comprise: carbonylating an epoxide with carbon monoxide toproduce at least one beta-lactone monomer; polymerizing at least onebeta-lactone monomer to produce at least one polylactone; and blowing atleast one polylactone to produce the polylactone-based foam. In certainembodiments, the epoxide and/or carbon monoxide are biobased.

In some embodiments, the process for producing a foam may includeheating components comprising at least one polylactone. The process forproducing a foam may be further carried out by subjecting the heatedpolylactone composition to molding to give a foamed structure. In somevariations, the composition comprising the at least one polylactone isin the form of a resin.

Optionally, in some embodiments, the polylactone may have greater thanabout 60% by weight, greater than about 70% by weight, greater thanabout 80% by weight, greater than about 90% by weight, greater thanabout 95% by weight, or greater than about 99% by weight biobasedcontent, for example.

Optionally, in some embodiments, the polylactone is a polypropiolactoneor an end-capped polypropiolactone. In some embodiments, thepolypropiolactone or end-capped polypropiolactone has a molecular weightof between about 40,000 g/mol and about 1,000,000 g/mol, or betweenabout 50,000 g/mol and about 500,000 g/mol, or between about 60,000g/mol and about 400,000 g/mol, or between about 70,000 g/mol and about300,000 g/mol, or between about 80,000 g/mol and about 150,000 g/mol,for example.

In some variations, the reaction vessel is charged with the at least onepolylactone. In certain embodiments, the reaction vessel may comprise anextruder, such as a twin-screw extruder. The extruder may have an insidetemperature from about 10° C. to about 160° C. and an inside pressurefrom about 10 bar to about 15 bar, for example.

Optionally, in some embodiments, carbon dioxide, such as supercriticalcarbon dioxide or nitrogen, for example, may be used as a blowing agentin the foam production. In some embodiments, pentane, isopentane, orcyclopentane, for example, may be used as a blowing agent in the foamproduction.

Optionally, in some embodiments, the composition may further comprise anucleating agent. Optionally, in some embodiments, the composition mayfurther comprise additives, such as those selected from the groupconsisting of: antioxidants, light stabilizers, fibers, foamingadditives, electrically conductive additives, antiblocking agents,antistatic agents, heat stabilizers, impact modifiers, biocides,compatibilizers, tackifiers, colorants, coupling agents, branchingagents, curing agents, and pigments, for example.

In another embodiment, a foam composition may comprise a compostablepolylactone. In some variations, the compostable polylactone has thefollowing repeating unit:

In some embodiments, the compostable polylactone comprises n repeatingunits, wherein n is from about 4,000 to about 1,000,000. In otherembodiments, the compostable polylactone has one or more end groups. Incertain embodiments, the one or more end groups are independentlyselected from the group consisting of: H, alkyl, alkenyl, alkoxy,alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, ester, amine, aniline,and amide.

In other variations, the compostable polylactone has the followingstructure:

wherein n is from about 4,000 to about 1,000,000; L₁ and L₂ may beindependently selected the group consisting of H, alkyl, alkenyl,alkoxy, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, ester, amine,aniline, and amide.

Definitions of specific functional groups and chemical terms aredescribed in more detail below. The chemical elements are identified inaccordance with the Periodic Table of the Elements, CAS version,Handbook of Chemistry and Physics, 75^(th) Ed., inside cover, andspecific functional groups are generally defined as described therein.Additionally, general principles of organic chemistry, as well asspecific functional moieties and reactivity, are described in OrganicChemistry, Thomas Sorrell, University Science Books, Sausalito, 1999;Smith and March March's Advanced Organic Chemistry, 5^(th) Edition, JohnWiley & Sons, Inc., New York, 2001; Larock, Comprehensive OrganicTransformations, VCH Publishers, Inc., New York, 1989; Carruthers, SomeModern Methods of Organic Synthesis, 3^(rd) Edition, CambridgeUniversity Press, Cambridge, 1987.

The term “alkyl” as used herein refers to saturated, straight- orbranched-chain hydrocarbon radicals derived from an aliphatic moietycontaining between one and six carbon atoms by removal of a singlehydrogen atom. Unless otherwise specified, alkyl groups contain 1-12carbon atoms. In some aspects, alkyl groups contain 1-8 carbon atoms. Insome aspects, alkyl groups contain 1-6 carbon atoms. In some aspects,alkyl groups contain 1-5 carbon atoms. In some aspects, alkyl groupscontain 1-4 carbon atoms. In yet other aspects, alkyl groups contain 1-3carbon atoms, and in yet other aspects alkyl groups contain 1-2 carbonatoms. Examples of alkyl radicals include, but are not limited to:methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl,sec-pentyl, iso-pentyl, tert-butyl, n-pentyl, neopentyl, n-hexyl,sec-hexyl, n-heptyl, n-octyl, n-decyl, n-undecyl, dodecyl, and the like.

As used herein, the term “partially unsaturated” refers to a ring moietythat includes at least one double or triple bond. The term “partiallyunsaturated” is intended to encompass rings having multiple sites ofunsaturation, but is not intended to include aryl or heteroarylmoieties, as herein defined.

As described herein, compounds may contain “optionally substituted”moieties. In general, the term “substituted”, whether preceded by theterm “optionally” or not, means that one or more hydrogens of thedesignated moiety are replaced with a suitable substituent. Unlessotherwise indicated, an “optionally substituted” group may have asuitable substituent at each substitutable position of the group, andwhen more than one position in any given structure may be substitutedwith more than one substituent selected from a specified group, thesubstituent may be either the same or different at every position.Combinations of substituents envisioned may include those that result inthe formation of stable or chemically feasible compounds. The term“stable”, as used herein, refers to compounds that are not substantiallyaltered when subjected to conditions to allow for their production,detection, and, in some aspects, their recovery, purification, and usefor one or more of the purposes disclosed herein.

In certain embodiments, the compostable polylactone is in the form of acompostable polylactone melt. In further embodiments, the compostablepolylactone melt may have greater than about 60% by weight, greater thanabout 70% by weight, greater than about 80% by weight, greater thanabout 90% by weight, greater than about 95%, or greater than about 99%biobased content, for example. Optionally, in some embodiments, thecompostable polylactone melt may have a temperature from about 10° C. toabout 160° C. and a pressure from about 10 bar to about 15 bar.

While this disclosure is susceptible to various modifications andalternative forms, specific exemplary embodiments thereof have beenshown by way of example in the drawings and have herein been describedin detail. It should be understood, however, that there is no intent tolimit the disclosure to the particular embodiments disclosed, but on thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the scope of the disclosure as defined bythe appended claims.

DETAILED DESCRIPTION

The following description sets forth exemplary processes, parameters andthe like. It should be recognized, however, that such description is notintended as a limitation on the scope of the present disclosure but isinstead provided as a description of exemplary aspects.

In some aspects, provided are polylactone-based foams comprising atleast one polylactone polymer.

In some variations, a “polymer” is a molecule of high relative molecularmass, the structure of which comprises the multiple repetition of unitsderived from molecules of low relative molecular mass. In some aspects,a polymer is comprised of only one monomer species. In some aspects, apolymer is a copolymer, terpolymer, heteropolymer, block copolymer, ortapered heteropolymer of one or more monomer species.

In certain preferred embodiments, the polylactone polymer comprises atleast one beta-lactone monomer. In certain preferred embodiments, atleast one beta-lactone monomer is produced via carbonylation of anepoxide with carbon monoxide. In certain embodiments, the epoxide and/orcarbon monoxide are biobased. In certain embodiments, thepolylactone-based foams may be produced from any of the beta-lactonesprovided in Column B of Table 1 below. As shown in Table 1 and in thefollowing chemical equation, such beta-lactones in Column B may beproduced from the corresponding epoxide listed in Column A of the table.

wherein R¹, R², R³, and R⁴ include any of the substituents from any ofthe structures in Table 1 below.

TABLE 1 Column A Column B

or/and

and/or

and/or

and/or

and/or

and/or

and/or

and/or

and/or

Preferably, in some embodiments, the polylactone polymers used in thepresent materials break down by composting. The degradationcharacteristics of the polylactone-based foam may be selected bymodifying the structure of the polylactone polymer chain, for example,by increasing or decreasing the number of ester groups in thepolylactone polymer chain.

The present invention describes compostable and/or biobased foams thatare useful for fabricating foamed articles. The foams of this inventionare produced using a compound comprising a compostable and/or biobasedpolylactone, such as a polypropiolactone or an end-cappedpolypropiolactone polymer and a blowing agent.

In some variations, an “end-capped polypropiolactone” comprises apolypropiolactone polymer that is reacted with one or more end-cappingagents to produce a thermally stable polymer. In some aspects, theend-capping agent is an aniline derivative selected from the groupconsisting of: benzothiazole, benzoxazole, benzimidazole,2-aminothiophenol, o-phenylenediamine, and 2-aminophenol. In otherembodiments, the end-capping agent is a phosphate selected from thegroup consisting of trimethylphospohate and triphenylphosphate. Suitableend-capping agents may even further include other additives andstabilizers such as isophthalic acid.

The compostable and/or biobased polylactone polymers may include thosepolylactone polymers that decompose into compounds having lowermolecular weight polylactones such as polypropiolactone.

In some embodiments, the polylactone may comprise polyacetolactone,poly-β-propiolactone, poly-γ-butyrolactone, and poly-δ-valerolactone,for example.

Preferably, in certain embodiments, the polylactone polymers used toproduce the foams of the present invention are biobased. For example,the polylactone polymers have greater than 20% biobased content, greaterthan 60% biobased content, more preferably greater than 70% biobasedcontent, more preferably 80% biobased content, more preferably 90%biobased content, more preferably 95% biobased content, and morepreferably 99% biobased content, for example.

The terms “bio-content” and “biobased content” mean biogenic carbon alsoknown as biomass-derived carbon, carbon waste streams, and carbon frommunicipal solid waste. In some variations, bio-content (also referred toas “biobased content”) can be determined based on the following:

Bio-content or Biobased content=[Bio (Organic) Carbon]/[Total (Organic)Carbon]*100%, as determined by ASTM D6866 (Standard Test Methods forDetermining the Biobased (biogenic) Content of Solid, Liquid, andGaseous Samples Using Radiocarbon Analysis).

For example, as disclosed in US 2017/0002136, the ASTM D6866 methodallows the determination of the biobased content of materials usingradiocarbon analysis by accelerator mass spectrometry, liquidscintillation counting, and isotope mass spectrometry. When nitrogen inthe atmosphere is struck by an ultraviolet-light-produced neutron, itloses a proton and forms carbon that has a molecular weight of 14, whichis radioactive. This ¹⁴C is immediately oxidized into carbon dioxide,and represents a small, but measurable, fraction of atmospheric carbon.Atmospheric carbon dioxide is cycled by green plants to make organicmolecules during photosynthesis. The cycle is completed when the greenplants or other forms of life metabolize the organic molecules andproduce carbon dioxide that is then able to return back to theatmosphere. Virtually all forms of life on Earth depend on thisgreen-plant production of organic molecules to produce the chemicalenergy that facilitates growth and reproduction. Therefore, the ¹⁴C thatexists in the atmosphere becomes part of all life forms and theirbiological products. These renewably based organic molecules thatbiodegrade to carbon dioxide do not contribute to global warming becauseno net increase of carbon is emitted to the atmosphere. In contrast,fossil-fuel-based carbon does not have the signature radiocarbon ratioof atmospheric carbon dioxide. See WO 2009/155086.

The application of ASTM D6866 to derive a “biobased content” is built onthe same concepts as radiocarbon dating, but without the use of the ageequations. The analysis is performed by deriving a ratio of the amountof radiocarbon (¹⁴C) in an unknown sample to that of a modern referencestandard. The ratio is reported as a percentage, with the units “pMC”(percent modern carbon). If the material being analyzed is a mixture ofpresent-day radiocarbon and fossil carbon (containing no radiocarbon),then the pMC value obtained correlates directly to the amount ofbiobased material present in the sample. The modern reference standardused in radiocarbon dating is a NIST (National Institute of Standardsand Technology) standard with a known radiocarbon content equivalentapproximately to the year AD 1950. The year AD 1950 was chosen becauseit represented a time prior to thermonuclear weapons testing whichintroduced large amounts of excess radiocarbon into the atmosphere witheach explosion (termed “bomb carbon”). The AD 1950 reference represents100 pMC. “Bomb carbon” in the atmosphere reached almost twice normallevels in 1963 at the peak of testing and prior to the treaty haltingthe testing. Its distribution within the atmosphere has beenapproximated since its appearance, showing values that are greater than100 pMC for plants and animals living since AD 1950. The distribution ofbomb carbon has gradually decreased over time, with today's value beingnear 107.5 pMC. As a result, a fresh biomass material, such as corn,could result in a radiocarbon signature near 107.5 pMC.

Petroleum-based carbon does not have the signature radiocarbon ratio ofatmospheric carbon dioxide. Research has noted that fossil fuels andpetrochemicals have less than about 1 pMC, and typically less than about0.1 pMC, for example, less than about 0.03 pMC. However, compoundsderived entirely from renewable sources have at least about 95 percentmodern carbon (pMC); they may have at least about 99 pMC, includingabout 100 pMC.

Combining fossil carbon with present-day carbon into a material willresult in a dilution of the present-day pMC content. By presuming that107.5 pMC represents present day biobased materials and 0 pMC representspetroleum derivatives, the measured pMC value for that material willreflect the proportions of the two component types. A material derived100% from present day biomass would give a radiocarbon signature near107.5 pMC. If that material were diluted with 50% petroleum derivatives,it would give a radiocarbon signature near 54 pMC.

A biobased content result is derived by assigning 100% equal to 107.5pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMCwill give an equivalent bio-based content result of 93%.

Assessment of the materials described herein according to the presentembodiments is performed in accordance with ASTM D6866 revision 12(i.e., ASTM D6866-12), the entirety of which is herein incorporated byreference. In some embodiments, the assessments are performed accordingto the procedures of Method B of ASTM-D6866-12. The mean valuesencompass an absolute range of 6% (plus and minus 3% on either side ofthe biobased content value) to account for variations in end-componentradiocarbon signatures. It is presumed that all materials are presentday or fossil in origin and that the desired result is the amount ofbiobased carbon “present” in the material, not the amount ofbio-material “used” in the manufacturing process.

Other techniques for assessing the biobased content of materials aredescribed in, for example, U.S. Pat. Nos. 3,885,155, 4,427,884,4,973,841, 5,438,194, and 5,661,299, and WO 2009/155086.

In some embodiments, the foams and the polylactone polymers used toproduce the foams described herein are obtained from renewable sources.In some variations, “renewable sources” include sources of carbon and/orhydrogen obtained from biological life forms that can replenish itselfin less than one hundred years.

In some embodiments, the foams and the polylactone polymers used toproduce the foams described herein have at least one renewable carbon.In some variations, “renewable carbon” refers to a carbon obtained frombiological life forms that can replenish itself in less than one hundredyears.

In some embodiments, the foams and the polylactone polymers used toproduce the foams described herein are obtained from recycled sources.In some variations, “recycled sources” include sources of carbon and/orhydrogen recovered from a previous use in a manufactured article.

In some embodiments, the foams and the polylactone polymers used toproduce the foams described herein have a recycled carbon. In somevariations, “recycled carbon” refers to a carbon recovered from aprevious use in a manufactured article.

Preferably, in other aspects, the polylactone polymers used herein maybe processed using conventional melt-processing techniques, such assingle and twin-screw extrusion processes. In one embodiment, foamedstructures are produced by cutting extrudate comprising biobasedpolylactone at the face of the extrusion die and subsequently optionallycooling by contacting with water, water vapor, air, carbon dioxide, ornitrogen gas.

In some variations, a “melt processable composition” comprises aformulation that is melt processed, typically at elevated temperatures,by conventional polymer-processing techniques, such as extrusion orinjection molding.

In some variations, “melt-processing techniques” includes extrusion,injection molding, blow molding, rotomolding, or batch mixing.

In some variations, an “extrudate” comprises the semisolid material thathas been extruded and shaped into a continuous form by forcing thematerial through a die opening.

Molded product material can be made by a variety of processes, includingblow molding, injection molding, open-pot molding, and thermoforming.Blow molding is employed to make hollow shapes, especially packagingcontainers. In an extrusion embodiment of this process, a parison ismade first and then expanded to the walls of the mold cavity.

Thermoforming is a branch of molding that uses thick films or sheets ofthermoplastic. Because polylactones may be easily converted to film orsheet forms that have excellent transparency, they are excellentcandidates for thermoforming. The sheet may be heated to the point thatit is quite flexible and then subjected to vacuum or pressure thatpresses the sheet against a mold, forming the desired shape. The plasticmemory of these polymer-plasticizer combinations is a useful attributein drape-forming embodiments of thermoforming.

In some embodiments, a plasticizer may be added or incorporated into thecomposition to address desired physical characteristics of the meltprocessable composition. In some variations, plasticizers includepolyalkylene glycols and functionalized naturally occurring oils. Insome variations, polyalkylene glycols include polyethylene glycols soldunder the Carbowax trade name (Dow Chemical Co., Midland, Mich.). Insome variations, functionalized naturally occurring oils includemalinated or epoxidized soybean, linseed, or sunflower oils.

In another embodiment, the compostable and/or biobased composition mayinclude a chain extender to increase the molecular weight of thecompostable or biobased polymer during melt processing. This also hasthe effect of increasing melt viscosity and strength, which can improvethe foamability of the compostable or biobased polymer. In somevariations, a “chain extender” comprises a material that, when meltprocessed with a polymer, increases the molecular weight by reactivelycoupling chain ends. An example of chain extenders useful herein includethose marketed under the CESA-extend trade name from Clariant, and thosemarketed under the Johncryl trade name from BASF.

In another aspect, the compostable and/or biobased melt-processablecomposition may contain other additives. In some variations, additivesinclude antioxidants, light stabilizers, fibers, blowing agents, foamingadditives, antiblocking agents, heat stabilizers, impact modifiers,biocides, compatibilizers, tackifiers, colorants, coupling agents,antistatic agents, electrically conductive fillers, and pigments.

In certain variations, the additives incorporated into the foam haveperformance-enhancing properties. For example, in one variation, theadditives include antioxidants and stabilizers that protect the foamfrom oxidative (or UV-induced) degradation; or light stabilizers thatprotect the material from light-induced degradation.

The additives may be incorporated into the melt-processable compositionin the form of powders, pellets, granules, or in any other extrudableform. The amount and type of additives in the melt-processablecomposition may vary depending upon the polymeric matrix and the desiredphysical properties of the finished composition. Those skilled in theart of melt processing are capable of selecting appropriate amounts andtypes of additives to match with a specific polymeric matrix in order toachieve the desired physical properties of the finished material.

In some variations, the biobased foams produced according to the methodsdescribed herein exhibit desirable properties in applications requiringvibration dampening, shock absorption, low weight, and buoyancy.

In another embodiment, more than about 60 wt % of the foam is producedfrom compostable materials, as determined by ASTM D6400. In a preferredembodiment, more than about 80 wt % of the foam is produced fromcompostable materials. In a most preferred embodiment, greater thanabout 95 wt % of the foam is produced from compostable materials.

The compostable polymers of this invention are produced by meltprocessing compostable polymers with a blowing agent and, optionally,additives that modify the rheology of the compostable or biobasedpolymer, including chain extenders and plasticizers.

In preferred embodiments, a polylactone polymer is combined with ablowing agent to produce a foam. The suitable blowing agents of thepresent invention are materials that can be incorporated into themelt-processable composition (e.g., the premix of the additives,polymeric matrix, and/or optional fillers, either in melt or solid form)to produce cells. The amount and types of blowing agents influence thedensity of the finished product by its cell structure. Any suitableblowing agent may be used to produce the foamed material.

In certain preferred embodiments, the blowing agents not incorporatedinto a polymer chain comprising beta-lactone monomers are termedphysical blowing agents. In certain embodiments, a physical blowingagent disperses polymer chains to produce cells. In a preferredembodiment, the physical blowing agent is carbon dioxide. In someembodiments, the physical blowing agent is uniformly distributed in amelt-processable composition with the polymer to provide a uniformcellular structure. In certain embodiments, the physical blowing agentsinclude one or more carbonate salts such as sodium, calcium, potassium,and/or magnesium carbonate salts. Preferably, sodium bicarbonate is usedbecause it is inexpensive and it readily decomposes to form carbondioxide gas. Sodium bicarbonate gradually decomposes when heated aboveabout 120° C., with significant decomposition occurring betweenapproximately 150° C. and approximately 200° C. In general, the higherthe temperature, the more quickly the sodium bicarbonate decomposes. Anacid, such as citric acid, may also be included in the foaming additive,or added separately to the melt-processable composition, to facilitatedecomposition of the blowing agent.

In certain other embodiments, blowing agents include water; carbonatesalts and other carbon-dioxide-releasing materials; diazo compounds andother nitrogen-producing materials; carbon dioxide; decomposingpolymeric materials such as poly(t-butylmethacrylate) and polyacrylicacid; alkane and cycloalkane gases such as pentane and butane; inertgases such as nitrogen, and the like. The blowing agent may behydrophilic or hydrophobic. In one embodiment, the blowing agent may bea solid blowing agent. In another embodiment, the blowing agent mayinclude one or more carbonate salts such as sodium, potassium, calcium,and/or magnesium carbonate salts. In yet another embodiment, the blowingagent may be inorganic. The blowing agent may also include sodiumcarbonate and sodium bicarbonate, or, alternatively, sodium bicarbonatealone.

Although the blowing agent composition may include only the blowingagent, in other embodiments, the blowing agent includes a polymericcarrier that is used to carry or hold the blowing agent. This blowingagent concentrate may be dispersed in the polymeric carrier fortransport and/or handling purposes. The polymeric carrier may also beused to hold or carry any of the other materials or additives that aredesired to be added to the melt-processable composition.

The inclusion levels of the blowing agent in the concentrate may varywidely. In some embodiments, foams include at least about 2.5 wt % ofblowing agent, at least about 5 wt % of blowing agent, or, suitably, atleast about 10 wt % of blowing agent. In other embodiments, foams mayinclude from about 10 wt % to about 60 wt % of blowing agent, from about15 wt % to about 50 wt % of blowing agent, or, suitably, from about 20wt % to about 45 wt % of blowing agent. In yet further embodiments, thefoaming additive may include from about 0.05 wt % to about 90 wt % ofblowing agent, from about 0.1 wt % to about 50 wt % of blowing agent, orfrom about 1 wt % to about 26 wt % of blowing agent.

As mentioned previously, the blowing agent concentrate may also includea polymeric carrier or material that is used to hold the other additivesto form a single additive. The polymeric carrier or polymeric componentmay be any suitable polymeric material such as hydrocarbon ornon-hydrocarbon polymers. The polymeric carrier should be capable ofbeing melted or melt processed at temperatures below the activationtemperature of the blowing agent. In some instances, however, apolymeric component having a melting point above the activationtemperature of the blowing agent may be used as long as it is processedquickly enough so that a suitable amount of active blowing agentremains. In one embodiment, the polymeric carrier has a melting point ofno more than about 150° C., no more than about 125° C., no more thanabout 100° C., or, suitably, no more than about 80° C. In a preferredembodiment, the blowing agent concentrate contains a compostable orbiobased polymer.

In certain preferred embodiments, one or more chemical blowing agentsmay react with one or more polymer chains to produce a gas suitable fordispersing the polymer chains to produce cells.

In some variations, the blowing agent is injected into the extruder inthe zone before the polymer melt is passed through the die. In certainvariations, the blowing agent is fed as a pressurized liquid, mixed intothe polymer melt and allowed to degas and foam as the melt exits theextruder.

In some variations, moldability of the compositions described herein canbe improved by adding a nucleating agent. The dispersion of a nucleatingagent within the polymer mixture helps in forming a uniform cellstructure. In some variations, a “nucleating agent” comprises a materialthat is added to a polymer melt that provides sites for crystalformation. For example, a higher degree of crystallinity and moreuniform crystalline structure may be obtained by adding a nucleatingagent. In certain variations, the foams produced according to themethods described herein have a crystallinity of at least 50%, at least60%, at least 70%, at least 80%, at least 90%, or at least 95%; orbetween 50% and 99%, or between 60% and 95%.

Examples of nucleating agents include inorganic powders such as: talc,kaolin, mica, silica, calcium carbonate, barium sulfate, titanium oxide,aluminum oxide, clay, bentonite, and diatomaceous earth, and knownchemical blowing agents such as azodicarbodiamide. Among them, in onevariation, talc is preferred because it may facilitate control of thecell diameter. The content of the nucleating agent varies depending onthe type of the nucleating agent and the intended cell diameter.

The amount of components in the melt-processable, compostable and/orbiobased foam composition may vary depending upon the intended end-useapplication. The final composition may comprise from about 40 wt % toabout 99 wt % of a compostable or biobased polymer. The blowing agentmay be included in the final composition at a level of up to about 20 wt%. The final composition may comprise from about 1 wt % to about 50 wt %of a compostable or biobased plasticizer. The final composition maycomprise from about 0.1 wt % to about 10 wt % of a chain extender.Nucleating agents (such as talc) can be included in the finalcomposition up to about 5 wt %, more preferably less than about 1 wt %,and most preferably about 0.5 wt %.

The physical blowing agent, such as supercritical carbon dioxide, iscombined with the melt early in the extruder mixing process. Then, asthe mixture exits the extruder and is cut, the supercritical carbondioxide expands to form the foamed structures. Optionally, heating ofthe foamed structures during a secondary expansion process allows forexpansion of the material to lower density.

In the extrusion foaming process, the temperature profile of theextruder must be carefully controlled to allow for: melting and mixingof the solids, reaction with the chain-extension agent (optional),mixing with blowing agent (for example, supercritical CO₂), and coolingof the melt mixture prior to extrusion through the die. The temperaturesof the initial barrel sections allow for melting and mixing of thesolids, including the dispersion of nucleating agent within the melt. Atthe same time, the optional chain-extension agent reacts with the chainends of the polymer, increasing branching and molecular weight, whichincreases viscosity of the melt and improves the melt strength of theplastic. Prior to injection of the blowing agent, a melt seal is createdwithin the extruder by careful design of internal screw elements toprevent the flow of the blowing agent from exiting the feed throat. Themelt seal maintains pressure within the extruder, allowing the blowingagent to remain soluble within the melted plastic. After injection ofthe blowing agent, mixing elements are used to mix the blowing agentwith the melt. Soluble blowing agent within the melt plasticizes themelt dramatically, greatly reducing its viscosity. The plasticizationeffect allows for the cooling of the melt to below the normal meltingtemperature of the compostable or biobased polymer in the final sectionsof the extruder. The cooling is necessary to increase the viscosity ofthe plasticized melt, allowing for retention of a closed cell structureduring foaming at the die.

Nucleating agents serve as nucleation sites for blowing-agent evolutionduring foaming. When depressurization occurs at the die, the blowingagent dissolved in the plastic melt comes out of solution into the gasphase. By entering the gas phase, the volume occupied by the blowingagent increases dramatically, producing a foamed structure. Bydispersion of the nucleating agent in the melt, the blowing agent willevenly evolve from its soluble state within the melt to its gaseous formduring depressurization, thus producing a fine cellular foam. Withoutproperly dispersed nucleation sites, the foaming can be uneven,producing large voids or open cell structure, where cell walls arefractured and interconnected. Large voids and open cell structurecreates a harder, more brittle foam. Very low density foams with closedcell structure can be described as spongy, having a good elasticrecovery after significant compression.

As extrudate exits the die and is foamed, rotating knives of thepelletizer cut the bead at the face of the die. When cut, the foam isnot completely established. The foaming process continues to shape thestructure of the bead after it has been cut. The blowing agent continuesto evolve, expanding the particle. The outer skin of the particleremains rubbery while cut, allowing the surface of the foamed bead toflow and reform a smooth, solid surface.

The melt-processable, compostable or biobased foam composition of theinvention can be prepared by any of a variety of ways. For example, thecompostable or biobased polymer, blowing agent, nucleating agent, andoptional additives can be combined together by any of the blending meansusually employed in the plastics industry, such as with a mixingextruder. The materials may, for example, be used in the form of apowder, a pellet, or a granular product. The mixing operation is mostconveniently carried out at a temperature above the melting point orsoftening point of the polymer. The resulting melt-blended mixture canbe processed into foamed structures by cutting the extrudate mixture ofpolymer and blowing agent at the face of the extrusion die. By cuttingthe extrudate at the face of the extrusion die, a bead is formed beforecomplete expansion of the foam has occurred. After pelletization, afoamed bead is formed from expansion of the extrudate by the blowingagent. The foamed bead cools by the release of blowing agent, butsubsequent cooling can be applied by contacting with water, water vapor,air, carbon dioxide, or nitrogen gas. The resulting foamed structurescan be molded into a three-dimensional part using conventional equipmentutilized in molding expandable polystyrene. In one embodiment, thefoamed structures contain residual blowing agent and can bepost-expanded in the molding process. In another embodiment, the foamedstructures are pressurized with a gas, such as air or carbon dioxide,before molding to allow for expansion during molding.

Melt processing typically is performed at a temperature from about 80°C. to about 300° C., although optimum operating temperatures areselected depending upon the melting point, melt viscosity, and thermalstability of the composition. Different types of melt processingequipment, such as extruders, may be used to process the meltprocessable compositions of this invention. Extruders suitable for usewith the present invention are described, for example, by Rauwendaal,C., “Polymer Extrusion,” Hansen Publishers, p. 11-33, 2001.

The first two examples below utilize a single type of polylactone resin.It is known, however, that the degree of crystallinity in polylactone iscontrolled by two general aspects: first, by composition, and second, byprocess. Polylactone is selected from the group consisting of apolypropiolactone and an end-capped polypropiolactone.

All crystallinity is lost when the plastic is heated above its meltingpoint, and a slow thermal annealing is required to inducecrystallization. Fillers, such as high-performance talcs, are often usedto promote a more rapid crystallization, yet most extrusion applicationsthat are hoping to take advantage of high crystallinity for thermalstability will require an annealing step between 100° and 130° C. tosufficiently crystallize the PPL. However, in the extrusion foamapplication, there is sufficient shear and elongation during generationof the foam to induce crystallinity within the very thin films ofplastic separating the closed cells of the foam. In addition, nucleatingagents used to promote dispersion and nucleation of CO₂ dissolved intothe melt during foam processing also improve crystallization kinetics.Therefore, the extrusion foam process induces rapid crystallization ofPPL. From the perspective of thermal stability, this is fortuitousbecause no annealing step is required.

In certain aspects, the foams produced according to the methodsdescribed herein can be reprocessed into a film or thermolyzed toacrylic acid, for example, to make superabsorbent polymers.

As used herein, the term “about” preceding one or more numerical valuesmeans the numerical value ±5%. It should be understood that reference to“about” a value or parameter herein includes (and describes) aspectsthat are directed to that value or parameter per se. For example,description referring to “about x” includes description of “x” per se.

Further, it should be understood that reference to “between” two valuesor parameters herein includes (and describes) aspects that include thosetwo values or parameters per se. For example, description referring to“between x and y” includes description of “x” and “y” per se.

The mass fractions disclosed herein can be converted to wt. % bymultiplying by 100.

ENUMERATED EMBODIMENTS

The following enumerated embodiments are representative of some aspectsof the invention.

1. A process for producing a foam, comprising the steps of heating acomposition containing at least one polylactone derived from a bio-basedcontent in a reaction vessel; and subjecting the heated polylactonecomposition to molding to give a foamed structure.

2. The process of embodiment 1, wherein at least one polylactone isselected from the group consisting of a polypropiolactone and anend-capped polypropiolactone.

3. The process of embodiment 2, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about40,000 g/mol and about 1,000,000 g/mol.

4. The process of embodiment 2, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about50,000 g/mol and about 500,000 g/mol.

5. The process of embodiment 2, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about60,000 g/mol and about 400,000 g/mol.

6. The process of embodiment 2, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about70,000 g/mol and about 300,000 g/mol.

7. The process of embodiment 2, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about80,000 g/mol and about 150,000 g/mol.

8. The process of embodiment 1, wherein the reaction vessel comprises anextruder.

9. The process of embodiment 8, wherein the extruder comprises atwin-screw extruder.

10. The process of embodiment 8, wherein the extruder has an insidetemperature from about 10° C. to about 160° C. and an inside pressurefrom about 10 bars to about 15 bars.

11. The process of embodiment 1, wherein carbon dioxide or nitrogen isused as a blowing agent in the molding.

12. The process of embodiment 11, wherein supercritical carbon dioxideis used as a blowing agent in the molding.

13. The process of embodiment 1, wherein pentane, isopentane, orcyclopentane is used as a blowing agent in the molding.

14. The process of embodiment 1, further comprising the step of mixingthe polymeric material with a blowing agent.

15. The process of embodiment 1, further comprising the step of chargingthe reaction vessel with at least one polylactone.

16. The process of embodiment 1, wherein the polylactone has greaterthan about 60% by weight biobased content.

17. The process of embodiment 1, wherein the polylactone has greaterthan about 70% by weight biobased content.

18. The process of embodiment 1, wherein the polylactone has greaterthan about 80% by weight biobased content.

19. The process of embodiment 1, wherein the polylactone has greaterthan about 90% by weight biobased content.

20. The process of embodiment 1, wherein the polylactone has greaterthan about 95% by weight biobased content.

21. The process of embodiment 1, wherein the polylactone has greaterthan about 99% by weight biobased content.

22. The process of embodiment 1, wherein the composition furthercomprises a nucleating agent.

23. The process of embodiment 1, wherein the composition furthercomprises one or more additives selected from the group consisting ofantioxidants, light stabilizers, fibers, foaming additives, electricallyconductive additives, antiblocking agents, antistatic agents, heatstabilizers, impact modifiers, biocides, compatibilizers, tackifiers,colorants, coupling agents, branching agents, curing agents, andpigments.

24. A composition, comprising:

a compostable polylactone melt processed with at least one blowing agentinto a mixture wherein the blowing agent is injected into the melt andthe mixture is extruded into a foamed structure.

25. The composition of embodiment 24, wherein at least one blowing agentis selected from the group consisting of pentane, isopentane,cyclopentane, carbon dioxide, and nitrogen.

26. The composition of embodiment 24, wherein the at least one blowingagent is supercritical CO₂.

27. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 60% by weight biobased content.

28. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 70% by weight biobased content.

29. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 80% by weight biobased content.

30. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 90% by weight biobased content.

31. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 95% by weight biobased content.

32. The composition of embodiment 24, wherein the compostablepolylactone melt has greater than about 99% by weight biobased content.

33. The composition of embodiment 24, wherein the polylactone isselected from the group consisting of a polypropiolactone and anend-capped polypropiolactone.

34. The composition of embodiment 33, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about40,000 g/mol and about 1,000,000 g/mol.

35. The composition of embodiment 33, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about50,000 g/mol about 500,000 g/mol.

36. The composition of embodiment 33, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about60,000 g/mol and about 400,000 g/mol.

37. The composition of embodiment 33, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about70,000 g/mol about 300,000 g/mol.

38. The composition of embodiment 33, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about80,000 g/mol and about 150,000 g/mol.

39. The composition of embodiment 24, further comprising a nucleatingagent.

40. The composition of embodiment 24, further comprising one or moreadditives selected from the group consisting of antioxidants, lightstabilizers, fibers, foaming additives, electrically conductiveadditives, antiblocking agents, antistatic agents, heat stabilizers,impact modifiers, biocides, compatibilizers, tackifiers, colorants,coupling agents, branching agents, curing agents, and pigments.

41. The composition of embodiment 24, wherein the compostablepolylactone melt has a temperature from about 10° C. to about 160° C.and a pressure from about 10 bars to about 15 bars.

42. A composition, comprising:

an extrudate of a compostable polylactone derived from a biobasedcontent containing a blowing agent wherein the extrudate is of aviscosity and density suitable for forming a foam with substantialstability and durability.

43. The composition of embodiment 42, wherein the blowing agent isselected from the group consisting of pentane, isopentane, cyclopentane,carbon dioxide and nitrogen.

44. The composition of embodiment 42, wherein the blowing agent is supercritical CO₂.

45. The composition of embodiment 42, wherein the extrudate has greaterthan about 60% by weight biobased content.

46. The composition of embodiment 42, wherein the extrudate has greaterthan about 70% by weight biobased content.

47. The composition of embodiment 42, wherein the extrudate has greaterthan about 80% by weight biobased content.

48. The composition of embodiment 42, wherein the extrudate has greaterthan about 90% by weight biobased content.

49. The composition of embodiment 42, wherein the extrudate has greaterthan about 95% by weight biobased content.

50. The composition of embodiment 42, wherein the extrudate has greaterthan about 99% by weight biobased content.

51. The composition of embodiment 42, wherein the polylactone isselected from the group consisting of a polypropiolactone and anend-capped polypropiolactone.

52. The composition of embodiment 51, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about40,000 g/mol and about 1,000,000 g/mol.

53. The composition of embodiment 51, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about50,000 g/mol about 500,000 g/mol.

54. The composition of embodiment 51, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about60,000 g/mol and about 400,000 g/mol.

55. The composition of embodiment 51, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about70,000 g/mol about 300,000 g/mol.

56. The composition of embodiment 51, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about80,000 g/mol and about 150,000 g/mol.

57. The composition of embodiment 42, further comprising a nucleatingagent.

58. The composition of embodiment 42, further comprising one or moreadditives selected from the group consisting of antioxidants, lightstabilizers, fibers, foaming additives, electrically conductiveadditives, antiblocking agents, antistatic agents, heat stabilizers,impact modifiers, biocides, compatibilizers, tackifiers, colorants,coupling agents, branching agents, curing agents, and pigments.

59. A process for producing a foam, comprising:

polymerizing at least one beta-lactone monomer to produce at least onepolylactone; and blowing at least one polylactone to produce apolylactone-based foam.

60. The process of embodiment 59, further comprising carbonylating anepoxide with carbon monoxide to produce at least one beta-lactonemonomer.

61. The process of embodiment 60, wherein the epoxide and/or carbonmonoxide are comprised of biobased molecules.

62. The process of embodiment 59, wherein the at least one polylactoneis selected from the group consisting of a polypropiolactone and anend-capped polypropiolactone.

63. The process of embodiment 62, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about40,000 g/mol and about 1,000,000 g/mol.

64. The process of embodiment 62, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about50,000 g/mol and about 500,000 g/mol.

65. The process of embodiment 62, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about60,000 g/mol and about 400,000 g/mol.

66. The process of embodiment 62, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about70,000 g/mol and about 300,000 g/mol.

67. The process of embodiment 62, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about80,000 g/mol and about 150,000 g/mol.

68. The process of embodiment 59, wherein carbon dioxide or nitrogen isused as a blowing agent.

69. The process of embodiment 59, wherein supercritical carbon dioxideis used as a blowing agent.

70. The process of embodiment 59, wherein pentane, isopentane, orcyclopentane is used as a blowing agent.

71. The process of embodiment 59, further comprising the step of mixingthe polymeric material with a blowing agent.

72. The process of embodiment 59, wherein the polylactone has greaterthan about 60% by weight biobased content.

73. The process of embodiment 59, wherein the polylactone has greaterthan about 70% by weight biobased content.

74. The process of embodiment 59, wherein the polylactone has greaterthan about 80% by weight biobased content.

75. The process of embodiment 59, wherein the polylactone has greaterthan about 90% by weight biobased content.

76. The process of embodiment 59, wherein the polylactone has greaterthan about 95% by weight biobased content.

77. The process of embodiment 59, wherein the polylactone has greaterthan about 99% by weight biobased content.

78. The process of embodiment 59, wherein the composition furthercomprises a nucleating agent.

79. The process of embodiment 59, wherein the composition furthercomprises one or more additives selected from the group consisting ofantioxidants, light stabilizers, fibers, foaming additives, electricallyconductive additives, antiblocking agents, antistatic agents, heatstabilizers, impact modifiers, biocides, compatibilizers, tackifiers,colorants, coupling agents, branching agents, curing agents, andpigments.

80. A foam composition, comprising:

a compostable polylactone having the following repeating unit:

wherein n is from about 4,000 to about 1,000,000, L1 and L2 areindependently selected the group consisting of H, alkyl, alkenyl,alkoxy, alkynyl, cycloalkyl, cycloalkenyl and cycloalkynyl, ester,amine, aniline, and amide.

81. The composition of embodiment 80, wherein the compostablepolylactone is selected from the group consisting of a polypropiolactoneand an end-capped polypropiolactone.

82. The composition of embodiment 81, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about40,000 g/mol and about 1,000,000 g/mol.

83. The composition of embodiment 81, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about50,000 g/mol about 500,000 g/mol.

84. The composition of embodiment 81, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about60,000 g/mol and about 400,000 g/mol.

85. The composition of embodiment 81, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about70,000 g/mol about 300,000 g/mol.

86. The composition of embodiment 81, wherein the polypropiolactone orend-capped polypropiolactone has a molecular weight of between about80,000 g/mol and about 150,000 g/mol.

87. The composition of embodiment 80, wherein the polylactone hasgreater than about 60% by weight biobased content.

88. The composition of embodiment 80, wherein the polylactone hasgreater than about 70% by weight biobased content.

89. The composition of embodiment 80, wherein the polylactone hasgreater than about 80% by weight biobased content.

90. The composition of embodiment 80, wherein the polylactone hasgreater than about 90% by weight biobased content.

91. The composition of embodiment 80, wherein the polylactone hasgreater than about 95% by weight biobased content.

92. The composition of embodiment 80, wherein the polylactone hasgreater than about 99% by weight biobased content.

EXAMPLES

The following Examples are merely illustrative and are not meant tolimit any aspects of the present disclosure in any way.

Several acronyms and abbreviations are used throughout this section. Forclarity, the most commonly used are presented here: polypropiolactone(“PPL”); beta-propiolactone (“bPL”).

Example 1

A dry mix blend of resin is produced consisting of approximately 99% byweight of end-capped polypropiolactone with molecular weight (“MW”) fromabout 80,000 g/mol to about 150,000 g/mol, and approximately 1% byweight of Cereplast ECA-023 talc masterbatch. The dry mix of resin isfed gravimetrically into the feed throat section of a twin-screwextruder (about 11 mm to about 25 mm barrel diameter). The feed rate forthe solids is set to 3.5 kg/hr (7.7 lbs/hr), and the screws are rotatingat 40 rpm. Carbon dioxide (CO₂) is blown into the plastic melt in thefourth barrel section of the extruder at 10 g/min. A single-slit diewith a 3 mm opening is bolted to the end of the extruder.

Initially, a flat temperature profile at 110° C. is used. Upon start-up,the extrudate is allowed to reach temperatures higher than 110° C. Atthe high temperatures, the foaming properties, melt strength, viscosityto hold onto the blowing agent, and cell structure is determined for theextrudate. The temperature profile over the nine barrel sections fromfeed to exit is systematically adjusted to achieve 10° C., 50° C., 80°C., 110° C., 110° C., 110° C., 110° C., 110° C., and 110° C. across theextruder. At these conditions, the melt pressure at the die isconfigured to be from about 10 bar to about 15 bar.

Example 2

A dry mix blend of resin is produced consisting of approximately 99% byweight of PPL with MW from about 80,000 g/mol to about 150,000 g/mol,and approximately 1% by weight of Cereplast ECA-023 talc masterbatch.The dry mix of resin is fed gravimetrically into the feed throat sectionof a twin-screw extruder (about 11 mm to about 25 mm barrel diameter).The feed rate for the solids is set to 3.5 kg/hr (7.7 lbs/hr), and thescrews are rotating at 40 rpm. End-capping agents (phosphate, such astrimethylphosphate and triphenylphosphate; benzothiazole; benzoxazole;benzimidazole; 2-aminothiophenol; o-phenylenediamine; and 2-aminophenol)are injected in the third barrel section of the extruder. The amount ofend-capped polypropiolactone made in-situ inside the extruder isdetermined. Carbon dioxide (CO₂) is blown into the plastic melt in thefourth barrel section of the extruder at 10 g/min. A single-slit diewith a 3 mm opening is bolted to the end of the extruder.

Initially, a flat temperature profile at 110° C. is used. Upon start-up,the extrudate is allowed to reach temperatures higher than 110° C. Atthis high temperature, the foaming properties, melt strength, viscosityto hold onto the blowing agent, and cell structure are determined forthe extrudate. The temperature profile over the nine barrel sectionsfrom feed to exit is systematically adjusted to achieve 10° C., 50° C.,80° C., 110° C., 110° C., 110° C., 110° C., 110° C., and 110° C. acrossthe extruder. At these conditions, the melt pressure at the die is fromabout 10 bar to about 15 bar.

The embodiments described herein are not intended to be limited to theaspects shown, but are to be accorded the widest scope consistent withthe principles and features disclosed herein.

1-39. (canceled)
 40. A composition, comprising: a. a polylactone polymerbeing end-capped with a thermally stable compound; and b. one or moreblowing agents, wherein the composition is foam-able when heated andmixed.
 41. The composition of claim 40, wherein the one or more blowingagents includes one or more of water, carbonate salts, acarbon-dioxide-releasing materials, diazo compounds, nitrogen-producingmaterials, carbon dioxide, decomposing polymeric materials,poly(t-butylmethacrylate), polyacrylic acid, carbon dioxide, nitrogen,pentane, isopentane, cyclopentane, or a combination thereof.
 42. Thecomposition of claim 40, further comprising one or more nucleatingagents.
 43. The composition of claim 40, wherein the one or morenucleating agents includes one or more of talc, kaolin, mica, silica,calcium carbonate, barium sulfate, titanium oxide, aluminum oxide, clay,bentonite, diatomaceous earth, or azodicarbodiamide, or any combinationthereof.
 44. The composition of claim 40, further comprising one or moreadditives including one or more of antioxidants, light stabilizers,fibers, foaming additives, electrically conductive additives,antiblocking agents, antistatic agents, heat stabilizers, impactmodifiers, biocides, compatibilizers, tackifiers, colorants, couplingagents, curing agents, or pigments, or any combination thereof.
 45. Thecomposition of claim 40, further comprising one or more chain extendersor one or more branching agents.
 46. The composition of claim 40,wherein the polylactone polymer is polypropiolactone, polylactide,polyglycolide, or polycaprolactone.
 47. The composition of claim 40,wherein the polylactone polymer comprises repeating monomers ofbeta-lactone derivatives.
 48. The composition of claim 40, furthercomprising one or more plasticizers including one or more ofpolyalkylene glycols, malinated soybean, epoxidized soybean, linseed,sunflower oils, or any combination thereof.
 49. The composition of claim40, wherein when the composition is heated and extruded, the compositionis an extrudate having a viscosity and density suitable for forming astable and durable foam.
 50. A foam, comprising: a. a polylactonepolymer being end capped by a thermally stable compound; and b. one ormore blowing agents.
 51. The foam of claim 51, wherein the one or moreblowing agents includes one or more of water, carbonate salts, acarbon-dioxide-releasing materials, diazo compounds, nitrogen-producingmaterials, carbon dioxide, decomposing polymeric materials,poly(t-butylmethacrylate), polyacrylic acid, carbon dioxide, nitrogen,pentane, isopentane, cyclopentane, or a combination thereof.
 52. Thefoam of claim 51, further comprising one or more nucleating agents. 53.The foam of claim 51, wherein the one or nucleating agents includes oneor more of talc, kaolin, mica, silica, calcium carbonate, bariumsulfate, titanium oxide, aluminum oxide, clay, bentonite, diatomaceousearth, or any combination thereof.
 54. The foam of claim 51, furthercomprising one or more additives including one or more of antioxidants,light stabilizers, fibers, foaming additives, electrically conductiveadditives, antiblocking agents, antistatic agents, heat stabilizers,impact modifiers, biocides, compatibilizers, tackifiers, colorants,coupling agents, curing agents, branching agents, chain extenders,plasticizers, pigments, or any combination thereof.
 55. The foam ofclaim 51, wherein the foam has a closed cell structure.
 56. The foam ofclaim 51, wherein the foam is thermolyze-able to produce acrylic acid.57. A process, comprising: heating an end-capped polylactone to producepolylactone melt; and processing the polylactone melt to produce a foam.58. The process of claim 57, wherein prior to heating, the processfurther comprises combining the end-capped polylactone with one or morenucleating agents, one or more additives, or any combination thereof.59. The process of claim 57, wherein after heating and prior to molding,the process further comprises adding one or more blowing agents to thepolylactone melt.